Thousands of Twitter users have received emails warning their account has been compromised by a third party.

Some accounts had been compromised, but other users had received the
emails after Twitter had unintentionally reset unaffected passwords, the
company said.

The mass email
coincided with incidents involving several high-profile accounts,
including at least one account belonging to the BBC.

Other media organisations, such as the TechCrunch blog, reported being warned.

Twitter gave no indication of the cause or source of the compromise, and would not share details of the size of the issue.

In a statement, it said: "When we believe an account may have been
compromised, we reset the password and send an email letting the account
owner know this has happened along with information about creating a
new password. This is a routine part of our processes to protect our
users.

"In this case, we unintentionally reset passwords of a
larger number of accounts, beyond those that we believed to have been
compromised.

"We apologise for any inconvenience or confusion this may have caused."

Deletions and spam

Some users who received the email noticed that some of their tweets had
been deleted, while others said spam links had been posted without
their knowledge - a typical characteristic of a compromised account.

The Twitter account belonging to BBC Radio 4's Today programme earlier
told followers it was "trying to get to the bottom" of problems relating
to their feed.

Other BBC accounts have received the warning email - but it is not yet clear if any more were compromised.

Comedian David Mitchell tweeted that he had received the email, and
that a tweet he had written publicising his column in the Observer
newspaper had been removed.

Some users criticised Twitter's
email, suggesting it looked like a "phishing scam" - a message that
impersonates an official email in an attempt to trick users into giving
up personal details.